I need help with subtracting or adding with variables kind of like this
@echo off
set var=5
echo %var%
pause
echo ___________________________________________
set /a %var% +1
echo %var%
Pause
Can you help me?

Well, I will, if I can. Where is that question?
In the meanwhile, I provided a reference to a very useful batch which you can use to learn batch programming or get reference information. Please see my answer; hope it will help you.
--SA